Design a Stack With Increment Operation

class EnhancedStack {
private:
    vector<int> dataStack;
    vector<int> lazyIncrement;
    int stackTop;

public:
    EnhancedStack(int maxSize) {
        dataStack.resize(maxSize);
        lazyIncrement.resize(maxSize);
        stackTop = -1;
    }

    void push(int x) {
        if (stackTop < (int)(dataStack.size()) - 1) {
            dataStack[++stackTop] = x;
        }
    }

    int pop() {
        if (stackTop == -1) {
            return -1;
        }

        int value = dataStack[stackTop] + lazyIncrement[stackTop];

        if (stackTop > 0) {
            lazyIncrement[stackTop - 1] += lazyIncrement[stackTop];
        }

        lazyIncrement[stackTop] = 0;
        stackTop--;
        return value;
    }

    void addIncrement(int k, int val) {
        if (stackTop >= 0) {
            int limit = min(stackTop, k - 1);
            lazyIncrement[limit] += val;
        }
    }
};

For the given problem title "Design a Stack With Increment Operation", the C++ code implements an enhanced stack capable of not only standard push and pop operations but also a custom "increment" operation to efficiently increase the bottommost elements of the stack.

• Initialization:

  • The EnhancedStack class is initialized with a specified maxSize. It uses two vectors: dataStack to store stack elements and lazyIncrement to manage increments for each position.
  • stackTop keeps track of the current top index of the stack, starting from -1 indicating the stack is empty.

• Push Operation:

  • The push method checks if there is room to add an element (i.e., stackTop is less than the maximal index of dataStack). If so, increments stackTop and assigns the new item to that position.

• Pop Operation:

  • The pop method first checks if the stack is empty. If not, it computes the value at stackTop by combining the base stack value and the increment stored at the same index.
  • Before decrementing stackTop, it propagates the increment value to the next element in the stack (if present). This lazy propagation ensures that only necessary computations occur, thereby enhancing efficiency.
  • Resets the increment at stackTop and returns the calculated value.

• Increment Operation:

  • The addIncrement method increases elements from the base of the stack up to a given count (k). It uses the lazyIncrement vector for efficient range updating by adjusting the increment at the minimal index between stackTop and k-1.

This intelligently designed class efficiently manages increments to collections of elements at the stack's bottom with minimal computations, making the stack operations highly optimized for scenarios where frequent increment adjustments are needed alongside regular pushes and pops.

class EnhancedStack {
    private int[] elements;
    private int[] increments;
    private int stackTop;

    public EnhancedStack(int maxSize) {
        elements = new int[maxSize];
        increments = new int[maxSize];
        stackTop = -1;
    }

    public void push(int value) {
        if (stackTop < elements.length - 1) {
            elements[++stackTop] = value;
        }
    }

    public int pop() {
        if (stackTop < 0) {
            return -1;
        }
        
        int poppedValue = elements[stackTop] + increments[stackTop];

        if (stackTop > 0) {
            increments[stackTop - 1] += increments[stackTop];
        }

        increments[stackTop] = 0;
        stackTop--;
        return poppedValue;
    }

    public void increment(int k, int value) {
        if (stackTop >= 0) {
            int maxIncrementIndex = Math.min(stackTop, k - 1);
            increments[maxIncrementIndex] += value;
        }
    }
}

The given Java code defines an EnhancedStack class designed to implement a stack with an additional increment operation. This feature-rich stack allows standard functionality like push and pop operations, along with the ability to increment the bottom k elements of the stack by a specified value in a single operation.

Functionality Breakdown:

• Initialization:

  • The EnhancedStack is initialized with a maxSize that determines the capacity of the stack.
  • Two arrays, elements and increments, are used where elements stores the actual stack elements and increments aids in the increment operation.
  • stackTop is an index tracking the top element of the stack.

• Push Operation:

  • Adds a new element to the top of the stack if there's available space.
  • Increases the stackTop index accordingly.

• Pop Operation:

  • Returns and removes the top element of the stack.
  • Applies any accrued increments to the popped element.
  • Propagates this increment to the next element if the stack isn't empty after the pop, ensuring any subsequent pops consider earlier increments.

• Increment Operation:

  • Efficiently increases the bottom k elements' value by the given increment without iterating over the elements.
  • The increments array tracks increments at relevant positions, utilizing the propagation method during pops to apply these increments.

This implementation ensures all operations (push, pop, and increment) are efficiently handled, making it suitable for scenarios requiring swift stack manipulations with additional complex operations like the bottom element increments. The use of an increments array for deferred increment application optimizes the increment operation, especially for large stacks.

class StackContainer:
    def __init__(self, limit: int):
        self._elements = [0] * limit
        self._increments = [0] * limit
        self._currentIndex = -1

    def push(self, value: int) -> None:
        if self._currentIndex < len(self._elements) - 1:
            self._currentIndex += 1
            self._elements[self._currentIndex] = value

    def pop(self) -> int:
        if self._currentIndex == -1:
            return -1

        top_value = self._elements[self._currentIndex] + self._increments[self._currentIndex]
        
        if self._currentIndex != 0:
            self._increments[self._currentIndex - 1] += self._increments[self._currentIndex]
        self._increments[self._currentIndex] = 0
        self._currentIndex -= 1
        return top_value

    def increment(self, count: int, increment_value: int) -> None:
        if self._currentIndex >= 0:
            position = min(self._currentIndex, count - 1)
            self._increments[position] += increment_value

This Python solution describes the implementation of a custom stack class StackContainer with the capability to support normal stack operations and an additional increment operation. The class manages stack operations with the following methods:

• __init__(self, limit: int):

  • Initializes the stack with two arrays, _elements for stack values and _increments for holding increments applicable to elements, based on a specified size limit.
  • A _currentIndex pointer is used to track the top element of the stack.

• push(self, value: int) -> None:

  • Adds a new element value to the top of the stack if there is space (i.e., _currentIndex is less than the top boundary of the stack).

• pop(self) -> int:

  • Removes the top element from the stack and returns its value, including any increments.
  • Adjusts the increment values so that the next top element, if available, receives the accumulated increments from the popped element.

• increment(self, count: int, increment_value: int) -> None:

  • Applies an increment_value to the bottom count elements of the stack. If count exceeds the number of elements in the stack, the increment is applied up to the last element.

This implementation efficiently handles the increment operation in a way that does not require iterating over all elements every time an increment is applied; instead, it strategically updates increment values, adding computational efficiency in scenarios where there are frequent increment operations.